Hosts England got the ball rolling yesterday evening and, for the rest of the week, much of the focus of the debate around the Rugby World Cup will centre on selection.

Yet perhaps the choices that will have most bearing on the way the pool stages proceed were made back on July 1 when World Rugby made their referee appointments for the tournament.

Like it or not, the man in the middle has more influence over how a rugby match goes than in most sports.

The identity of the officials has a huge bearing on the way a game will be played, with each of the high-level referees coming with their own set of expectations and focusing on different areas of the game.

Celebrity referees are a rarity in other sports, but rugby embraces their officials like few others. Nigel Owens' charisma and compelling back story helps, but there are not many other officials in sport who are such well-known public figures.

When Ireland take on France at the Millennium Stadium on October 11, there will be Irish fans who are more familiar with the Welsh whistler than some of the players on the pitch.

His celebrity is indicative of a game where the officials are more prominent than they should be, but it is a fact of life that they will have a major influence in the coming weeks.

Back in June, World Rugby issued referees with a list of tweaks and areas of focus that were in play during the Rugby Championship and the warm-up internationals to allow players to get used to the changes in time for the main event.

The emphasis on straight feeds into the scrum is unlikely to be followed, while tightening up the competition under the high ball was simply enshrining what had been seen during last season. The tightening up of the tackle area and a subtle change to the maul, though, will have an effect on Ireland.

In their third warm-up game against Wales, Ireland got on the wrong side of Craig Joubert leaving Joe Schmidt particularly unhappy after his side conceded an uncharacteristic 14 penalties and two free-kicks.

Perhaps the most notable penalty came when Paul O'Connell was whistled for cleaning out Welsh flanker Justin Tipuric around the neck, something covered under World Rugby's assertion that "cleanouts around the neck must be penalised".

Ireland disputed the call, but it was an example of the focus that has been placed on the area. With defensive players clamping on to the ball in the 'jackal' position, arriving support players try to roll their opponents off as best they can, but it can be dangerous.

Ireland openside Sean O'Brien said: "You would look at any ruck over the last couple of years and someone always has someone around the neck trying to get him on the ground, pull him over or flip him over.

"You can't go near someone's neck now. That's the way it is. You have to be very conscious of that. You just make sure you're on the money discipline-wise at game time.

"We will work to make sure that's not in our game anymore."

Similarly, referees are becoming stricter on defensive players supporting their own body weight at the ruck and not placing their hands on the ground before contesting for the ball.

Ulster's Rory Best noted: "You could see even over the last weekend in the PRO12 that they're trying to clean up the tackle area in terms of the tackler using his arms and also just the breakdown.

"The referee wants it a lot cleaner in there, the tackle release."

The maul is another area of Ireland's strength that has seen some change, with the referees watching for players joining from behind the ball and stopping defending players 'swimming' through the maul and getting their hands on the ball.

Devin Toner explained: "One of the main things is that they don't want people joining ahead of the ball-carrier. So one of the main things we've worked on is that. Simon (Easterby) is big on being on the right side of the law, so we have had to do a good amount of mauling exercises.

"We've done a fair bit on that, on not coming in from the side and (referees) don't like players swimming over the top, he doesn't like players becoming detached and then going back on to it, so we're trying to work on that."

Under Schmidt, Ireland have generally managed to stay onside of referees, but there have been occasions where they have failed to find favour with the officials.

In particular, they appeared to lose Wayne Barnes' good-will during their Six Nations defeat to Wales in Cardiff, with the English ref becoming annoyed by the amount of back-chat coming from the green ranks.

Over the weekend, Scotland great John Jeffrey, who now chairs the game's Laws Representation Group, said back-chat would be clamped down on and Best believes Ireland are ready to zip it.

"When you've as talismanic a captain as we have in Paul O'Connell, he has been refereed by all of the referees two, three, maybe even more times so he knows what to say and when to say it," he said.

"Something that Joe pushes is it's all about the next moment. If a decision goes against you, there's no use pleading to the referee. He's not going to change his mind and, if anything, the next 50-50 decision is probably going to swing a little against you."

Schmidt is a keen disciplinarian and will have been hammering home the message this week. Staying onside with referees is half the battle and is a pillar of Ireland's success.